1. Field of the Invention
This invention relates to a method of extracting out certain sulfonated organic compounds from alcohols used to prepare said compounds.
2. Description of the Prior Art
Organic sulfonic acids and organic sulfonates are becoming increasingly important due to their use in the preparation of liquid detergents, as surfactants for enhanced oil recovery processes and for other uses. A number of general schemes are available to sulfonate organic compounds. For example, sulfonated materials may be prepared by sulfonation processes employing concentrated sulfuric acid or oleum. Another method of preparing organic sulfonates involves reacting an organic alcohol containing at least one hydroxyl group with a hydroxy-containing alkyl sulfonic acid or salt thereof. Under appropriate conditions the two compounds are condensed with formation of by-product water to produce an ether sulfonate. This reaction can be termed a sulfoalkylation reaction. A typical sulfonating reagent here used to react with a wide variety of organic alcohols is sodium isethionate, also named as the sodium salt of 2-hydroxy ethane sulfonic acid.
In most instances it is necessary to separate out the sulfonate produced or anionic surfactant from the reaction mixture which normally contains unreacted starting materials such as the alcohol reactant. In the above case wherein an alcohol is reacted with a sulfonating agent such as sodium isethionate usually an excess of alcohol is employed to assist in driving the reaction to completion. Thus, it is necessary to resolve the mixture of starting alcohol material and final ether sulfonate, one from the other.
There are a number of ways available to effect such separation. However, with respect to surfactants of relatively high molecular weight usually an extraction technique is devised. The use of such extractants in the usual situation is at best an emperical type of science faced with much unpredictability. For example, a class of extractant materials useful in separating one group of nonionic surfactants from anionic surfactants derived therefrom may be entirely useless in making a similar resolution, though of only a slightly different class of surfactants.
In other situations while a solvent may be found useful as an extractant in certain situations, such solvent while displaying proper selectivity may have other drawbacks such as itself being unstable, or having a tendency to convert the materials being separated to other derivatives by chemical reaction, which derivatives may be corrosive or have other undesirable properties. In still further instances, the extraction may require heat, causing formation of emulsions or gels. Lastly, while a solvent may be useful as an extractant, in many instances the solvent itself is difficult to separate out from the material it has extracted, and in some cases is impossible to do so.
It is therefore a principle object of this invention to provide a method for separating out ether sulfonates from organic alcohols from which ether sulfonates were derived through reaction with hydroxy-containing alkyl sulfonic acids or salts by means of a unique extraction technique, which process is free from the just-mentioned disadvantages of prior art processes.
The above-mentioned object and advantages of the present invention will become apparent as the invention is more thoroughly discussed hereinafter.